1. Field of Invention
The present invention relates to a liquid crystal display. More particularly, the present invention relates to a multi-directional diffusion-symmetric slant reflector (DSSR).
2. Description of Related Art
Liquid crystal displays (LCD) consume very little power in addition to being light and thin. Therefore, a LCD is incorporated into most mobile information processing equipment. To reserve battery power in the mobile equipment, the LCD must consume as little power as possible. Because a conventional transmissive type of LCD requires a backlight, a large amount of the battery power is used just to illuminate the LCD panel. A reflective type of LCD utilizes surrounding light and hence has very low power consumption. Hence, a reflection LCD is highly suitable for mobile equipment.
FIG. 1 is a schematic cross-sectional view showing a conventional reflective type of LCD. As shown in FIG. 1, the LCD has a planar reflector composed of an upper panel 102 and a lower panel 100. Light 104 coming from one side is reflected by the planar reflector. Notice that after reflecting from the planar reflector, the direction having the brightest reflection amongst the diffused rays 106 coincides with the direction of the normal reflection of the light ray 104 on a planar mirror. That is, the reflected light ray 108 having peak intensity is in a direction symmetrical to the incoming light ray 104. Because the peak intensity is not in the observer""s direction 110, the brightness level of the surrounding light is not fully utilized.
FIG. 2 is a schematic cross-sectional view of another conventional reflective type of LCD. In FIG. 2, an asymmetric slant reflector 112 is used. Light 104 coming from one side is reflected by the asymmetric slant reflector 112. Although this design can align the brightest portion of the reflection with the observer""s viewing direction 110, the asymmetric design of the reflector often leads to a variation of light intensity according to the viewing angle.
In yet another conventional reflective type of LCD, bump structures are formed on the surface of the reflector. Although the bumps are able to smooth out the non-uniformity of light intensity according to the viewing direction, the brightest portion of the reflected light also is not aligned with the observer""s viewing direction. Consequently, the surrounding light is not fully utilized, similar to a conventional planar reflector.
The present invention is provides a multi-directional diffusion-symmetric slant reflector (DSSR). The DSSR is capable of guiding the brightest portion of reflected light toward the viewing direction of the observer. The multi-directional diffusion-symmetric slant reflector is capable of smoothing out light intensity across a wide range of viewing angles. Furthermore, a method of forming a multi-direction diffusion-symmetric slant reflector compatible with current manufacturing practices is provided.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a multi-directional diffusion-symmetric slant reflector. A substrate having a plurality of domains thereon is provided. A plurality of diffusion-symmetric slant reflectors is formed on the substrate. The diffusion-symmetric slant reflectors can have a variety of shapes including cone, elliptical cone, longitudinal prism or other polyhedron shapes. In addition, a plurality of bumps, such as cone, elliptical cone, longitudinal prism structures, are formed on the slant surface of the diffusion-symmetric slant reflectors. The longitudinal prismatic and elliptical cone diffusion-symmetric slant reflectors within a domain of the substrate are aligned to a direction particular to that domain. An reflection layer such as an aluminum layer, a silver layer or a layer made of materials with a characteristic of reflection, is formed over the surface of the diffusion-symmetric slant reflector.
The invention also provides a method of forming a diffusion-symmetric slant reflector. A substrate is provided, and then a photoresist layer is formed over the substrate. After the substrate and photoresist layer assembly are baked, a photolithographic process is conducted using a gray-level mask, a multi-step exposure process or a half-tone mask. The exposed photoresist layer is developed, followed by an intermediate baking and a hard baking. In the final step, aluminum is deposited over the photoresist layer.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.